Preparation And Properties Of Hydroxyapatite/Silk Fiber/Chitosan Composite Porous Material

As a natural polymer biomaterial,silk fibroin is widely used in the field of biological tissue engineering because it contains essential amino acids and excellent mechanical properties.The chitosan is the only cationic alkaline polysaccharide in nature,has the advantages of degradability,antibacterial and osteoconductivity,and promoting bone growth.This paper uses silk short fiber as a reinforcing material ang chitosan as a matrix material to prepare silk short fiber/chitosan/hydroxyapatite ternary composite scaffold by biomineralization.First of all,this topic studied the biomineralization behaviors of the bombyx mori silk fiber and tussah silk fiber.SEM,TG,FTIR,XRD and XPS were used to characterize the two kinds of silk fibers before and after mineralization,and the impact of the morphology,structure and mineralization speed of silk fibers were studied for different types of silk fibers and different mineralization durations.Experimental results showed two kinds of silk fibers could be used as mineralization template to form calcium-deficient hydroxyapatite on its surface;tussah silk fiber contains more acidic amino acids and the carboxyl groups on acidic amino acids can make it combine with Ca²⁺to form mineralization nucleation sites.Therefore,the mineralization rate of tussah fiber was faster.Then,this topic used freeze-drying method to prepare a three-dimensional porous structure of tussah silk short fibers/chitosan binary composite scaffold.SEM,FTIR,XRD and texture analyzer were used to characterize the morphology and mechanical properties of the composite porous scaffold.The experimental results show that the pore size and porosity of the pure chitosan porous scaffold are 245.4±36.5?m and 69.0±0.8%,respectively,and the pore wall surface is smooth;with tussah silk short fiber content increasing,the pore size and porosity of the composite porous scaffold show a trend of increasing first and then decreasing,and the pore structure is composed of short fibers and chitosan.The addition of tussah silk short fibers significantly improves the mechanical properties of the composite porous scaffold:as the short fiber content increases,the compressive strength of the composite porous scaffold increases;when the short fiber content is 200%,the compressive stress is11.4±0.7 k Pa in the wet state,and the compressive stress can reach 220.0±11.7 k Pa in the dry state.The compressive strength of the pure chitosan porous scaffold in the wet and dry state is 1.3±0.2 k Pa and 93.8±8.5 k Pa,respectively.That is to say,the addition of short fibers greatly improves the mechanical properties of the porous scaffold.Considering comprehensively,the chitosan porous materials with short fiber content of 0%,75%and200%were selected for the next experiment.Finally,the tussah silk short fiber/chitosan binary composite scaffold was prepared into the tussah silk short fiber/chitosan/hydroxyapatite ternary composite scaffold by the simulated body fluid mineralization.SEM,TG,FTIR,XRD and texture analyzer were used to characterize the morphology,structure and properties of the hydroxyapatite/tussah silk short fiber/chitosan composite porous scaffold.The experimental results show that after the composite porous scaffold is mineralized,a relatively uniform mineralized layer is deposited on the surface of the pore wall,and the pore size is reduced;the thermal stability of the composite porous scaffold after mineralization is enhanced;and the deposition of the mineralized layer has also significantly improved the mechanical properties of the composite porous scaffold.